Researchers at IIT Bombay have made significant progress in developing an oxidation-resistant, nickel-based superalloy for ultra-efficient boilers in coal-fired thermal power plants. The alloy, known as Alloy 617, has shown the ability to withstand extreme temperatures and pressures, making it suitable for use in the most efficient boilers. This advancement is a milestone in the evolution of Advanced Ultra Super Critical (AUSC) technology, which aims to maximize efficiency and reduce carbon emissions.
The current hierarchy of boiler technologies starts with subcritical boilers, which operate at around 570 degrees Celsius and 175 bars of pressure, achieving an efficiency of 33-37 percent. Supercritical boilers, operating at 570 degrees Celsius and 250 bars, offer slightly higher efficiency of 38-42 percent. The next step is the ultra-supercritical boilers, which reach 620 degrees Celsius and 275 bars, with an efficiency range of 42-46 percent. However, the most efficient boilers are the AUSCs, operating at 710 degrees Celsius and 320 bars, with an efficiency exceeding 50 percent.
India, in its plans to add 87 GW of coal-fired power plants by 2032, aims to adopt the best available technologies to maximize energy output while minimizing environmental impact. The introduction of AUSC boilers, which produce more electricity with lower carbon emissions, is a crucial step in this direction.
The primary challenge in developing high-efficiency boilers is finding materials that can withstand the extreme temperatures and pressures involved. The IIT Bombay research team, led by Prof VS Raja of the Department of Metallurgical Engineering and Material Science, conducted tests on Alloy 617 in a simulated AUSC environment that replicated the conditions of a coal-fired power plant.
Prof Raja explained that the objective of the research was to understand the suitability of Alloy 617 for AUSC applications. While the alloy has shown promising resilience in extreme conditions, further work is needed to develop a fully functional boiler. The team also tested another alloy, Alloy 740, which exhibited better mechanical strength but oxidized at an earlier stage.
To manufacture Alloy 617, India may rely on the capabilities of the public sector alloy company, MIDHANI (Mishra Dhatu Nigam). The alloy used in the experiments was locally fabricated by Symec Engineers, making it a pioneering study in the country.
Experts in boiler design have lauded the research findings, emphasizing their significance in developing better boilers. Mr. M R Ganesan, a former Executive Director at BHEL, even recommended reviving the ‘magneto hydro dynamics’ project, which can generate power with significantly reduced carbon emissions.
The research conducted by IIT Bombay opens up new possibilities for the development of ultra-efficient boilers that can maximize energy output while minimizing environmental impact. As India continues to expand its coal-fired power capacity, adopting such advanced technologies becomes crucial in achieving sustainable and efficient energy production.
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